Rust (Ex): A rust monster that makes a successful touch attack with its antennae causes the target metal to corrode, falling to pieces and becoming useless immediately. The touch can destroy up to a 10-foot cube of metal instantly. Magic armor and weapons, and other magic items made of metal, must succeed on a DC 27 Reflex save or be dissolved. The save DC is Constitution-based and includes a +4 racial bonus.

A metal weapon that deals damage to a rust monster corrodes immediately. Wooden, stone, and other nonmetallic weapons are unaffected.